Tension control device



March 3, 1964 R. E. CLARK ETAL TENSION CONTROL DEVICE 3 Sheets-Sheet 1 Filed April 23, 1962 INVENTORS' R. A. 62/1 RX 0. M S/MEA a 61 13551. A fink/V5) March 1964 R. E. CLARK ETAL 3,123,31

TENSION CONTROL DEVICE Filed April 25, 1962 5 Sheets-Sheet 2 hvvz-w TORS R. t. CLARK J. V. SIMEK ,c. c. V5;

ATTORNF) R. E. CLARK ETAL 3,123,317

TENSION CONTROL DEVICE March 3, 1964 Filed April 25. 1962 5 Sheets-Sheet 3 .50 loo TENS/0N or 3700 (85) INVNTOR$ A. 5. CLARK J. V. S/ME/r H 6.6. VAL

C ATTORNEY United States Patent 3,123,317 TENSION CONTRUL DEVICE Richard E. Clark, Rushville, .lcrry V. Sirnelr, Berwyn,

and Charles C. Veale, West Chicago, Ill, assignors to Western Electric Company, incorporated, New York,

N .Y., a corporation of New York Filed Apr. 23, 1962, Ser. No. 189,336 Claims. (til. 24275.3)

This invention relates generally to a strip tensioning device, and more specifically to a tension control device for applying controlled tension to material during translation thereof so that predetermined tensile sresses are not exceeded in the material.

It is common practice, particularly in the spinning and reeling arts to employ a weighted roller member for continuously tensioning lengths of strip or stranded material during translation thereof from a source of supply or from the machine that produces the strip to the spinning machine or the take-up reel. When the strip of material is metallic the tensioning additionally serves the function of straightening out bends or kinks which may be present in the material.

The roller for tensioning the strip of material is usu ally mounted on one end of a pivotally mounted arm, the arm having a weight element attached thereto for biasing the roller against the strip. Since the mass is mounted for pivotal movement on the arm the force exerted by the roller against the strip varies as a function of the angular displacement of the mass, the roller applying a maximum force against the strip when the effect of the moment produced by the pivoting mass becomes maximum.

As the moment produced by the mass approaches a maximum value, the force applied against the strip by the roller becomes critical, and it has been observed by those working in the art that slight variations in the force applied by the roller to the strip may cause large increases in strip tension sufiicient in many instances to cause tensile failure of the strip.

It is broadly an object of this invention to provide a tension control device for opposing the effect of variably increasing tensioning forces applied by a weight-biased tensioning member to a strip of material so that predetermined tensile stresses are not exceeded in the strip.

More specifically it is an object of this invention to provide a tension control device for tensioning continuous lengths of material, the device providing a cam and a weight element for opposing the effect of variably increasing tensioning forces applied by a weight-biased tensioning roller to a strip of material so that predetermined tensile stresses are not exceeded in the strip, the device additionally including mechanism for initially statically and dynamically counterbalancing the cam and weight element.

According to this invention, a tension control device includes a tensioning roller over which the strip of material is looped, the roller being biased in one direction by a first weighted element and being displaced by variations in length of the strip loop resulting from variations in tensioning forces applied to the strip. The roller is connected to rotate a shaft upon displacement there of by variations in loop length. A cam is mounted on the shaft and a second weighted element is suspended from the cam for applying a torque to the shaft upon rotation of the cam in one direction. The periphery of the cam has a constant and a varying configuration for providing respectively a constant and a variable moment arm for the second weighted element upon rotation of the cam. The effective length of the variable moment arm increases so that the cam will dampen out the undesirable effect of oscillating displacements of the ten- "ice sioning roller as tensioning forces applied to the strip approach maximum value.

Other objects, advantages and novel aspects of the invention will become apparent upon reference to the following detailed description, taken in conjunction with the appended drawings, in which:

FIG. 1 is a front view of the tension control device embodying the present invention and showing some of the components thereof in one position;

FIG. 2 is a vertical sectional view of the device taken on the line 2-2 of FIG. 3 showing the components in another position;

FIG. 3 is a side View of the device shown in FIG. 1; and

FIG. 4 shows two curves which illustrate the relationship between the angular displacement of a weighted tensioning roller and the force applied to the strip by movement of that roller, one curve showing this relationship for prior art tensioning devices, the second curve showing the same relationship using the tensioning device of the instant invention.

Referring now to FIG. 1, a strip, web or strand of material 11 is drawn from a supply reel (not shown) or from the source producing the material (not shown) through the tensioning device 12 to mechanism such as a capstan (not shown) or a utilization machine. The strip 11 passes between a pair of coacting rollers 13 and 14, under a guide roller 15, over a tensioning roller 16 and under another guide roller 17 to the mechanism (such as a capstan) that draws the strip under tension from between the rollers 13 and 14.

The length of the strip loop formed by the rollers 15, 16 and 17 will vary as the force applied to the ends of the strip 11 vary and the roller 16 is moved in response to variations in loop length.

The roller 16 is mounted for rotative movement on a shaft 19, FIG. 3, the ends of the shaft 19 being secured in a slide 29 which is slidable in grooves 21 formed in vertical supports 22 and 23 of the frame 24. A tape 25 is ailixed to one end of the slide 25 the other end of the tape 25 being connected to a sheave 26 secured to a shaft 27. The shaft 27 is journaled for rotation in the frame 24 and vertical displacement of the tensioning roller 16 from the position shown in FIG. 1 to the position shown in FIG. 2 causes counterclockwise rotation of the sheave 26 and the shaft 27.

As shown in FIG. 3, a pendulum 29 having a weight 32' connected to one end thereof is connected at the other end to the shaft 27 by a pin 31. A pair of cams 32 and 33 are similarly connected to the shaft 27 for rotation therewith, the periphery of the cam 32, being grooved so that a tape or cord 35 connected to a weighted element 34 is seated in the periphery of the cam 32. The tape 35 is connected to the tip of the cam 32 (FIG. 1) by a pin 39. The radius of the cam 32 is constant over an interval of cam peripheral length and then increases in the direction of, and as a result of counterclockwise rotation of that cam. Thus, as a result of rotation of the sheave 26 the torque applied to the shaft 27 by the weighted element 34 is initially constant for a predetermined interval or period of cam 32 rotation and then varies in accordance with the posi tion of the cam 32, the position of the cam 32 being adjustable on the shaft 27 in order to provide any desired countertorque to the torque developed by the pendulum 29.

A scale 40 may be fixed to the frame 24 and a pointer 41 connected to the shaft 27 so thatangular displacement of the shaft 27 will be indicated on the scale 40 by the pointer 41.

As will be evident from FIGS. 1 and 2, the countertorque initially applied by rotation of the cam 32 to the shaft 27 is constant, and increases after the cam 32 and the pendulum 29 pivot through ninety degrees or more since the radius of the cam 32 increases at that period in the rotational cycle of the shaft 27. FIG. 2 shows the position of the rotated cam 32 just prior to its effecting an increase in the moment arm of the tape 35. As will be evident from a subsequent detailed analysis of the curves C and C illustrated in FIG. 4-, the contour of the cam 32 and the angular position thereof with respect to the pendulum 29 can be varied to provide a curve C slope tangent to any point on the curve C.

A sheave 36 and the cam 33 are secured to a common hub 37 connected to the shaft 27. -A tape or cord 38 is secured at one end thereof in the sheave 36 (FIG. 3), the other end of the tape 38 being connected to a weighted element M). The weighted elements 34 and 4t} have substantially the same mass, and the radius of the sheave "36 is substantially equal to the distance between the center of the shaft 27 and the constant radius portion of the cam 32. The cam 33 is a substantially exact replica of the cam 32 so that the moment of inertia of the cams 32 and 33 are preferably identical, the earns 32. and 33 being positioned in opposition so as to counterbalance each other on the shaft 27. The tension applied to the tape 38 by the weighted element 40 is such that tension control device '12 is statically balanced in the position shown in FIG. '1 and is dynamically balanced until the moment arm provided by the periphery of the cam 32 increases. As will be discussed in detail hereinafter, the additional torque produced by the weighted element 34 dampens out the effect of large forces that are applied by the tensioning roller 16 against the strip 11 as the loop formed by the roller and strip approaches a straight line.

As the tension in the strip 11 varies from a minimum to a maximum the vertical position of the roller 16 varies accordingly, FIG. '1 showing the position of the roller 16 when the tension in the strip 11 is minimum and FIG. 2 showing the position of the roller 16 as the tension in the strip 11 approaches a maximum value. As the position of the tensioning roller 16 varies, the angle 6 increases from zero to 180 degrees. The force applied to the shaft 27 by rotation of the pendulum 29' is nonlinear as can be seen from the curve C illustrated in FIG. 4.

Referring now to FIG. 4, the curve C is obtained by plotting pendulum displacements as a function of the tension in the strip 11 developed by the tensioning roller 16 against the strip 11 when the cams 32 and 3-3 and the associated weighted elements 34 and 40 are removed from the tensioning device 12. The device 12 would therefore consist of a tensioning roller biased by a weighted element, such as the pendulum 29, and would resemble a tensioning device of conventional type. As will be evident, the curve C approaches the horizontal abscissa in a nonlinear manner as the tensioning roller approaches the lower limit of vertical displacement (PEG. 2), the strip loop approaching a straight line as a result of maximum tensioning forces being applied thereto. As the angular displacement of the pendulum 29 increases and approaches 180 degrees, the effect of the force applied by the tensioning roller '16 against the strip '11 becomes critical. As the effect of the force applied by the tensioning roller becomes critical, it has been observed that slight oscillating movements in the tensioning roller produce large differentials of tension in the strip 11. Such oscillations may, for example, result from irregularities in the surface of the strip striking the tensioning roller, machine vibrations, and oscillations of the pendulum 29. As will be apparent from an examination of the curve C, large differentials in tension in the strip may cause the forces developed therein to exceed a maximum value, of for example, 200 lbs.

In comparison, the curve C is obtained when the earns 32 and 33 are employed and the weighted elements 34 and 40 connected thereto. Because of the variable countertorque applied by the statically and dynamically counterbalanced cam 32 and the weighted element 34, the curve C becomes essentially a linear function as the tensioning roller approaches the lowermost limit in vertical travel, and therefore the effect of oscillations of the roller 16 will be dampened out so that the force applied to the strip ill will become uniform and less critical.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of this invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. A tension control device for applying controlled tension to continuously moving material, the device comprising:

a roller mounted for reciprocable movement over which the material is looped, said roller being movable in response to variations in the length of the loop resulting from variations in the tension applied to the material;

a member having said roller connected thereto and mounted for rotative movement;

means connected to said member for applying a torque thereto upon rotation of said member caused by increases in the force applied to said roller by increases in the tension applied to the strip;

a cam connected to said member;

a weighted element connected to said cam for applying a countertorque to said member, said cam having a surface configuration for providing a constant and a variable moment arm for said Weighted element, the moment varying with respect to said member upon rotation of said cam through a predetermined angle, the length of the moment arm varying in accordance with the countertorque required for said weighted element to dampen out the efiect of oscillations of said roller as the loop length decreases; and

means connected to said member for dynamically coun terbalancing said cam and said weighted element until said cam rotates through said predetermined angle.

2. A tension control device for applying controlled tension to a continuously moving strip of material, the device comprising:

means for supporting the strip during movement produced by tension applied to the material;

a reciprocativeiy movable roller over which the material is looped, said roller bein movable in response to variations in the length of the loop resulting from variations in tension applied to the material;

a shaft having said roller connected thereto and mounted for rotative movement;

a first weighted element connected to said shaft for applying a torque to said shaft upon rotation of said shaft caused by increases in the force applied to said roller by increases in the tension applied to the material;

a cam secured to said shaft for rotation therewith for applying a countertorque thereto upon rotation of said cam in one direction, the periphery of said cam continuously increasing in radius with respect to the axis of said shaft in the direction of rotation of said shaft in said one direction so as to provide a moment arm which effectively increases in length;

a flexible connection having one end thereof connected to a point on the cam periphery, said connection contacting the cam periphery and extending substantially tangentially therefrom so that the distance between said connection and the axis of said shaft increases during cam rotation in said one direction; and

a second weighted element connected to the other end of said connection for producing a countertorque to the torque produced by said first weighted element,

the radius of said cam periphery being determined by the countertorque required for said second weighted element to dampen out the effect of oscil lations of said roller as the loop length decreases.

A tension control device for applying controlled tension to a continuously moving strip of material, the device comprising:

means for supporting the strip during movement produced by tension applied to the material;

a reciprocatively movable roller over which the material is looped, said roller being movable in response to variations in the length of the loop resulting from variations in tension applied to the material;

a shaft having said roller connected thereto and mounted for rotative movement;

first weighted element connected to said shaft for applying a torque to said shaft upon rotation of said shaft caused by increases in the force applied to said roller by increases in the tension applied to the material;

a first cam secured to said shaft for rotation therewith a flexible connection having one end thereof connected to a point on the cam periphery, said connection contacting the cam periphery and extending substantially tangentially therefrom so that the distance between said connection and the axis of said shaft increases during cam rotation in said one direction;

a second weighted element connected to the other end of said connection for producing a countertorque to the torque produced by said first weighted element, the radius of said cam periphery being determined by the countertorque required for said second weighted element to counter varying increases in force applied by the material to said roller;

a second cam connected to said shaft for counterbalancing said first cam, said second cam being substantially identical to said first cam and positioned on said shaft as to provide an equal and opposite moment of inertia;

a sheave connected to said shaft; and a third weighted element suspended from the periphery of said sheave for biasing said sheave in a direction opposite said one direction, the radius of the sheave periphery being substantially equal to the radius of said first cam over the constant radius interval, the mass of said third weighted element being substantially equal to the mass of said second Weighted element so that the device is dynamically counterbalanced by said second cam and said third weighted element during rotation of said first cam through said predetermined angle, the increase in the radius of said first cam determined by the countertorque required for said second weighted element to dampen out the effect of oscillations of said roller as the loop length decreases;

A device for applying tension to a moving strand of indefinite length comprising:

means including a pair of spaced rotary elements for supporting the moving strand and forming a loop therein between said elements;

roller for supporting the loop and tensioning the strand;

a first member having an arcuate supporting surface; means for mounting said first member for oscillatory movement about a horizontal axis concentric with said arcuate supporting surface;

means including a flexible member secured at one end to said first member and supported on and extending tangentially downwardly from said arcuate surface for supporting said roller;

a weighted element secured in fixed and eccentric relation to said first member for applying a torque thereto in one direction to urge the roller upwardly; cam mounted in fixed relation to said first member for oscillatory movement therewith and having an outer extremity spaced a substantial distance from said axis and having a concentric portion spaced a lesser distance from said axis and provided with a curved supporting surface extending from said extremity to and around said concentric portion; weight for imparting a countertorque to said first member; and

flexible member secured at one end to said extremity of said cam and supported on said curved supporting surface of said cam and extending downwardly therefrom to support said weight, said cam being angularly disposed about said axis in a predetermined relation to said weighted element so as to effect a relatively rapid increase in the countertorque by said weight as the weighted element is moved into a critical angular range about said axis.

A device as defined in claim 4 including:

second member secured in fixed relation to said first member for oscillatory movement therewith and having an arcuate supporting surface concentric with said axis;

a second weight; and

flexible member secured at one end to said second member and supported on said arcuate surface and extending downwardly therefrom to support said second weight so as to counterbalance said first mentioned weight.

References Cited in the file of this patent UNITED STATES PATENTS Karber Aug. 7, 1962 

1. A TENSION CONTROL DEVICE FOR APPLYING CONTROLLED TENSION TO CONTINUOUSLY MOVING MATERIAL, THE DEVICE COMPRISING: A ROLLER MOUNTED FOR RECIPROCABLE MOVEMENT OVER WHICH THE MATERIAL IS LOOPED, SAID ROLLER BEING MOVABLE IN RESPONSE TO VARIATIONS IN THE LENGTH OF THE LOOP RESULTING FROM VARIATIONS IN THE TENSION APPLIED TO THE MATERIAL; A MEMBER HAVING SAID ROLLER CONNECTED THERETO AND MOUNTED FOR ROTATIVE MOVEMENT; MEANS CONNECTED TO SAID MEMBER FOR APPLYING A TORQUE THERETO UPON ROTATION OF SAID MEMBER CAUSED BY INCREASES IN THE FORCE APPLIED TO SAID ROLLER BY INCREASES IN THE TENSION APPLIED TO THE STRIP; A CAM CONNECTED TO SAID MEMBER; 